Cache-Control header is not always allowed in the pre-flight request

[PulsarBlow]

Some APIs do not allow Cache-Control header

eg github api : Access-Control-Allow-Headers: Authorization, Content-Type, If-Match, If-Modified-Since, If-None-Match, If-Unmodified-Since, X-GitHub-OTP, X-Requested-With

Cache control should be handled with the If-Modified header